Recombinant human pp14 inhibits expression of IL-2 by jurkat cells

Placental protein 14 (PP14) is a glycoprotein produced by cells of the reproductive and hematopoietic systems that possesses antiinflammatory activity. A previous study has suggested that PP14 isolated from amniotic fluid can suppress IL-2 production in mixed lymphocyte cultures. To better define PP14's immunomodulatory potential, we have now produced recombinant human PP14 using a pET22b periplasmic expression vector. The his6-tagged PP14 was purified using Ni2-sepharose chromatography. The periplasmic (nonglycosylated) PP14 was shown to retain the immunoinhibitory function of native PP14 in a two-way mixed-lymphocyte reaction. The immunoinhibition could be reversed with polyclonal anti-PP14 antibody, verifying that the inhibition was mediated by PP14. Bypassing the complexities of peripheral blood mononuclear cell populations, we further showed that the recombinant PP14 could suppress IL-2 production by human Jurkat T cells stimulated with PMA plus anti-CD3 mAb. Hence, the data indicate that periplasmic PP14 can mediate IL-2 suppression and that the suppressive effect can be monitored in a T cell line. The mechanism of the IL-2 modulatory effect is under investigation.